Soil Management for Sustainable Agricultural

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Soil Management for Sustainable Agricultural Intensification in the Himalayan Region Roshan M. Bajracharya, Dil Prasad Sherchan, Bed Mani Dahal, and Nani Raut

CONTENTS 6.1 Introduction................................................................................................... 143 6.2 Impacts of Agricultural Intensification on the Environment......................... 145 6.3 Social and Economic Aspects of Intensive Agriculture................................ 149 6.4 Sustainable Agricultural Intensification........................................................ 150 6.4.1 Integrated Nutrient Management....................................................... 150 6.4.2 Crop Rotations and Cropping Patterns.............................................. 152 6.4.3 Biofertilization and Seed Inoculation................................................ 152 6.4.4 Minimum and Zero Tillage............................................................... 153 6.4.5 Biogas and Biochar............................................................................ 155 6.4.6 Microirrigation and Water Management........................................... 155 6.4.7 Other Holistic Management Approaches........................................... 156 6.5 Future Priorities for Food Security and Environmental Protection.............. 157 6.6 Conclusions.................................................................................................... 159 References............................................................................................................... 160

6.1 INTRODUCTION Soils have been and still are the primary medium for large-scale agricultural production upon which human civilizations have depended for sustenance and expansion. Over millennia, since the first human communities began settled agriculture, people have learned to manage and successfully cultivate their lands to produce the food required for nurturing modern societies and the development of their regions. Previously, communities were small and the demand on land and soil resources was low; hence, traditional agricultural practices could meet the needs of the population (Braidwood 1960; Piggot 1961). Following the industrial revolution in the 1800s, the world’s human population has grown tremendously, currently surpassing 143

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7 billion, with growth still rapid in the less developed countries of Asia, Africa, and the Middle East. Thus, while arable land has essentially reached the limits of expansion, pressures on the land resource base continue to increase with evergreater demands for food production. The need for producing higher amounts of food on the same amount of land has fuelled agricultural intensification. The Green Revolution of the post–World War II era enabled many advanced nations to dramatically increase crop yields and food production through the use of inorganic fertilizers and improved crop varieties. However, by the end of the 20th century, the impacts of intensified production systems, which relied heavily on man-made chemical fertilizers and pesticides, on the environment, as well as soil biophysical quality degradation, erosion, and fertility decline, could no longer be ignored (Thomas et al. 1956). As the nutritive requirements of a growing world population will only increase into the foreseeable future, sustainable agricultural intensification practices and technologies are indispensable. The development and adoption of such options will require concerted efforts on the parts of scientists, governments, and local farming communities merged through contextual knowledge systems. The application of integrated nutrient management has shown that optimum combinations of farmyard manure and inorganic fertilizers increased yields by 16%–35% in the mid-hills of Nepal. Similarly, a combination of compost and fertilizer gave significantly higher yields of wheat and potato crops over conventional farming. Combinations of different crops, such as pigeon pea and groundnut, have been shown to result in yield increases of maize of >100%, while leading to improved soil properties. Inoculation of seeds with Rhizobium strains have also been found to lead to yield increases of 40%–67% compared with noninoculated seeds for a variety of crops, such as soybean, lentils, black gram, groundnuts, and broad beans. Apart from crop and seed improvements, soil and water management options, such as conservation tillage, mulching, and microirrigation, are equally important in ensuring sustainable intensive production. Studies in the mid-hill region of the Himalaya have demonstrated that mulching and reduced tillage could lead to a reduction in soil and nutrient losses from upland farms by 46% to >100%, while increasing water retention and providing comparable crop yields. Thus, successful implementation of sustainable agricultural intensification to meet the growing global food demand will involve simultaneously addressing soil and land management, water use efficiency, crop and agrobiodiversity, and adequate policy and institutional support. Soil and land resources have been the backbone of human civilization ever since prehistoric communities of people established permanent settlements and began settled agriculture some 10 thousand or more years ago (Darlington 1969). Past civilizations, such as the ancient settlements of the Tigris–Euphrates and Nile River valleys, flourished as a direct consequence of having access to fertile soils, and likewise, declined as a result of degradation and loss of fertility of agricultural lands (Hillel 1992). Through the course of history, previous human communities learned to manage their soils and successfully cultivate their lands, even under rather harsh climates and terrains such as the arid region of Egypt and the mountainous regions of South Asia (Hillel 2007). Over the centuries, and particularly since the beginning of the Industrial Rev olution in the 1800s, the human population has seen a tremendous increase in growth


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rate. The 20th century saw the population doubling rates drop to 120,000 biogas plants have been installed in rural areas across Nepal, it could serve as an important component of sustainable farming systems while simultaneously helping conserve forests and reduce carbon dioxide and methane emissions to the atmosphere. Biogas slurry application was observed to increase the yields of maize, rice, wheat, and cabbage by 30%, 23%, 16%, and 25%, respectively, over the conventional farmer practice in the Nepal mid-hills (Karki 2004). Biochar is a subject of recent scientific investigation as a potential means of enhancing the carbon storage capacity and longevity in soils, while simultaneously increasing the soils’ fertility and productive capacity. Biochar, a pyrolysis product of biomass, has been used by ancient civilizations in the Amazon, northwest Europe, and the Andes (Sombroek et al. 1993; Sandor and Eash 1995; Downie et al. 2011). It has recently gained scientific attention as a simple yet potentially powerful tool for climate change mitigation while contributing to sustainable agricultural production (Downie et al. 2011; International Biochar Initiative 2012). The benefits of biochar reportedly result from its high stability, porosity, and resistance to microbial breakdown, thereby acting as sites for increased water and nutrient retention (Sohi 2012).

6.4.6 Microirrigation and Water Management Water management will no doubt be a subject requiring considerable attention and effort with climate change, erratic precipitation, and water scarcity becoming ever more acute in the years to come. Yet, to meet the increasing demands and livelihood security, farmers have opted to grow high-value and out-of-season vegetables such as tomatoes (Lycopersicon esculentum Mill.), cucumber (Cucumis sativus L.), squash (Cucurbita pepo L.), and cauliflower (Brassica oleracea L.). Such crops, however, are sensitive to water stress and require a regular, reliable supply of water (Wan and Kang 2006; Enciso et al. 2007). Under these conditions, drip or microirrigation offers a viable and waterefficient option for irrigating vegetable crops during periods of water scarcity. Drip or trickle irrigation is a type of microirrigation method intended for both water conservation and efficient use of water by the crop. Microirrigation systems deliver water in the form of drops, tiny streams, or miniature sprays directly to the plant root zone. Such systems may be placed on the soil surface or at varying depths in the crop bed (Schwab et al. 1993; Hla and Scherer 2003; Ensico et al. 2007). Microirrigation systems have the advantage of enabling economic crop yields with

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minimal use of water (Randhawa and Abrol 1990), as well as the control of nutrient levels, which can be supplied along with the irrigation water (Schwab et al. 1993; Hla and Scherer 2003). Such microirrigation techniques, together with water harvesting, will have to be exploited to the fullest extent if we are to meet agricultural water requirements under intensive crop production in the future.


6.4.7 Other Holistic Management Approaches Increasing the efficiency and productivity of agricultural systems while ensuring sustainability in the face of ever-increasing demands, will, undoubtedly require holistic, integrated approaches that incorporate environmentally sound land, water, crop, livestock, and pest management (Figure 6.3). Latif et al. (2005) compared three rice cultivation methods in the Comilla District of Bangladesh and found that the existing best management practice of the Bangladesh Rice Research Institute gave significantly better performance, higher yields, higher profit, and lower cost than the System of Rice Intensification or conventional farmer practice. These intensive practices and improved technologies may be site specific and have to be adjusted to local conditions. Other studies in China also indicated that integrated crop–soil management practices hold potential to increase crop yields without posing adverse environmental risks. Chen et al. (2011) used a hybrid–maize simulation model to determine the optimum combination of planting date, crop density, and plant variety to apply at a particular site based on long-term weather data. Nearly double the yield (13 Mg ha−1) of current farmer practice was obtained without increasing the nitrogen fertilizer dose. Thus, substantially

Improved soil and land management

Efficient water management and crop use

Sustainable intensification of agriculture

Better crop and pest management

Appropriate policies and institutions

FIGURE 6.3 Simultaneous measures needed to achieve sustainable agricultural intensification in the Himalayan region.



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improved yields, through soil and crop management, may be achieved by the right combination of genetically improved crop varieties coupled with better agronomic practices, in the face of deteriorating soil quality, increasing water shortages, and other uncertainties brought about by climate change (Fan et al. 2012). The Sloping Agricultural Land Technology proposed by Tacio (1993) uses an integrated and holistic approach through a combination of terracing, contour operations, fodder hedge rows, agroforestry, and mixed cropping. The approach, tailored to local conditions, is likely to be compatible with sustainable hill farming in the Himalayan region. Indeed a “whole landscape” approach, using place-specific strategies combining crop diversification and improved soil, crop, and livestock management, along with agroforestry, are likely needed to achieve sustainable land use through targeted policy and management interventions (DeFries and Rosenzweig 2010).

6.5 FUTURE PRIORITIES FOR FOOD SECURITY AND ENVIRONMENTAL PROTECTION It is amply evident that demands on land and water resources will continue to increase and that further intensification of agriculture will be required to meet global food demands in the future. Under the present trends of increased agricultural intensification in the richer nations and increased land clearing in poorer nations, it has been estimated that about 1 billion hectares of land would be cleared globally by 2050 with greenhouse gas emissions reaching about 3 Pg y−1 of CO2 equivalent and nitrogen use reaching approximately 250 Mt y−1 (Tilman et al. 2011). Local land use decisions can have global implications for terrestrial carbon stocks and global climate change in view of the food demands of a growing population, changing diets, and biofuel production. Tropical areas have been calculated to lose nearly twice as much carbon (about 3 Mg C per million grams of annual crop yield), while producing less than half the annual crop yields compared with temperate regions (West et al. 2010). Thus, special emphasis is needed on increasing yields from existing croplands in the tropics rather than clearing new lands. Agricultural intensification has been typically characterized by a synergy between agronomic innovations and plant breeding (Evans 2003). Globally, agricultural intensification has been able to keep pace with population growth through continuous evolution; it is estimated that about 2 million hectares of land are affected by soil erosion, 1.5 million hectares by salinization and toxification, and even greater amounts of land are permanently lost due to urban expansion onto arable land (Evans 2003). Therefore, more innovative, integrated, and sustainable production systems will be needed to keep pace with demands in the future. Genetically improved seeds and crops are already in use worldwide and likely to be an important part of agricultural sustainability. Hence, the use of high-yielding varieties enhanced through genetic modification is expected to be a crucial part of the solution to raise global yields without further degrading the environment (Ronald 2011). However, studies suggest that the expected future food demand cannot be met by increasing genetic yield potential alone as the gap between average farm yields and genetic potential is narrowing (Cassman 1999). Therefore, a combination of soil quality improvement along with greater precision in agricultural management choices (crop, nutrient,


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water, pest, etc.) will be needed, which will require breakthroughs in plant physiology, eco-physiology, agroecology, and soil science (Matson et al. 1997; Cassman 1999; Chen et al. 2011; Fan et al. 2012). The pressures on natural resources in the Himalayan region will most certainly be extreme due not only to the vast population but also to the delicate balance in which ecosystems of this region exist. Further exacerbating the uncertainty of future changes in productive capacity of the land are the escalating impacts of climate change. Thus, a four-pronged strategy, optimally integrating (i) improved soil and land management, (ii) increased water use efficiency and water resource management, (iii) crop and agrobiodiversity management, and (iv) appropriate policy and institutional support, will be necessary to meet the daunting challenge of sustainable agricultural intensification (Figure 6.3). The possible measures and technologies to be applied toward formulating the strategy are described in Table 6.7.

TABLE 6.7 Measures and Technologies Required to Achieve Sustainable Intensification of Agriculture in the Himalayan Region Resource Category Soil/land resource— improved soil management

Water resource management and use efficiency

Crop/agrobiodiversity resource management

Policy and institutional initiatives

Measures and Technologies • Enhanced soil fertility and quality through improved composting, use of adequate farmyard manure, and urine application • Increased soil organic matter and soil carbon sequestration • Use of biofertilizers and optimization of rhizosphere microbial activity • Use of biochar and zeolite amendments to improve soil biophysical properties and water retention • Adoption of reduced or minimum tillage, crop residue management, and other conservation practices • Increased water use efficiency through microirrigation and timing of application; use of laser level to improve irrigation/water productivity • Water harvesting and groundwater recharge • Improved water retention in soil through the application of biochar, zeolites, and mulching • Water recycling, wastewater reclamation and reuse, desalinization • More efficient and risk-averting crop production systems, such as agroforestry with high-value crops; mixed cropping, relay cropping, and intercropping • Improved crop varieties with drought, cold, and pest resistance; high-yielding varieties enhanced through genetic modification • Forage species/crop rotations and planting of fruit and fuel wood tree species on private land • Integrated and natural pest control approaches • Adequate investment in agricultural research • Technical support to farmers through extension and outreach services • Institutional support and strengthening of capacity • Policies and incentives to encourage conservation and sustainable production


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However, it is clear that scientists and farmers must work collaboratively, in a mutually reinforcing manner, to find the optimal strategies. Fruitful collaborations will indeed depend on the ability to build contextual knowledge systems enabling understanding of the complexities of the natural systems, farming systems, as well as the sociocultural fabric of the many diverse localities across the Himalayan region (Andersen 2005). This can be achieved by merging scientific knowledge systems with local knowledge systems and the appropriate incorporation of indigenous technical knowledge. It is only through such contextual knowledge that effective and self-perpetuating changes in agricultural and natural resource management will likely be adopted by the local land users (Bajracharya and Sherchan 2009).

6.6 CONCLUSIONS Ensuring adequate food production in the future will, without a doubt, involve further intensification of agriculture. Among the greatest challenges of modern times is the necessity to meet the ever-growing food demands with limited arable land resources and without causing irreversible damage to the environment in the face of increasing unpredictability due to global climate change (The Royal Society 2009; Lambin et al. 2011). Although agriculture has been generally regarded as a source of greenhouse gases, with intensification, the net emissions on a yield basis has avoided an estimated 161 Gt C despite increased emissions from fertilizer use (Burney et al. 2010). Therefore, it makes sense to invest in yield improvement through intensified cropping as a cost-effective option for avoiding greenhouse gas emissions that would occur owing to the production of the same amount of crops at previous lower yield rates. However, the transition to sustainability will clearly require a stable population and stable levels of material consumption (Ruttan 1999), and sound policies and innovations that harness globalization to increase land use efficiency rather than causing uncontrolled land use expansion (Lambin et al. 2011). This will require land systems to be modeled as open systems with large flows of goods, people, and capital connecting local land use with global-scale factors. Hence, the global-scale cascading effects of local land use decision could possibly be avoided through new forms of global governance linking trade with environmental protection (Lambin and Meyfoiydt 2011). Certainly then, maintenance of the capacity for institutional and technological innovations will be more critical than environmental constraints, which will require increased investments in agricultural research and alleviating poverty, food insecurity, and malnutrition in low-production-potential areas most at risk of environmental degradation (Pinstrup-Andersen and Pandya-Lorch 1994; Ruttan 1999; The Royal Society 2009). In the Himalayan region, attaining sustainable, intensified production will require an integrated and holistic approach encompassing improved soil management, increased water use efficiency, higher yielding varieties coupled with diversified cropping, and integrated plant nutrient and pest management backed by appropriate policy and institutional support. The combination of measures and technologies, such as reduced/minimum tillage, choice of cropping patterns and crop varieties, biofertilization, natural and biological pest control, microirrigation, and integrated

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crop–livestock agroforestry systems, will no doubt need to be matched to local conditions with increased precision and site specificity. Success in achieving such intensive and sustainable production systems will clearly depend on farmers, scientists, and policy makers working together in a synergistic manner for the benefit of society at present and in the future.


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